Posted Mon Aug 13, 2012, 6:12pm Subject: Chemex filter size and using them in an Aeropress

OK, I just wanted to put this up on the internet since I couldn't find it anywhere high and low when I looked and was too bashful to ask. Now I got the filters (FSU-100). opened up they are rectangular and measure about 11 3/8 inches by 12 inches (LXW). You can make sixteen from one sheet for an aeropress. I found a glass which had the same diameter of the aeropress filters, got a pizza box and Xacto razor knife and made sixteen in three minutes. Just put the Chemex filter as it comes folded (it is folded to a quarter of its spread size by two midline folds). The Xacto knife, with a lot of pressure on the glass so nothing moved cut right through all four layers and made four filters each time. You get used to putting that sort of pressure on a glass after pushing the Aeropress a few times so a piece of cake.

As for results, I have a great Colombian organic coffee at its peak timing, like six days since roasting, and used one of these unbleached glass-pizza fabricated filters and side by side then a regular aeropress filter. The Chemex filter worked fine and really didn't feel like a much heavier stock than the Aeropress beached filters, and the liquid went right though as normal - it was easy, which I didn't expect with all the heavier, thicker, etc. comments.

For the flavor, I hate to say it, but I preferred the cheap regular filter. I don't know if there is something funky going on with putting the pores under a bit of pressure, but actually preferred the regular filter taste. Felt like more good oils were removed, but don't hold me to it; they were prepared identically in identical timing and concentration, but the chemex filter left what I considered a weaker with even a thinner mouthfeel.

First, everywhere says that Chemex filters are tougher to penetrate and slow the flow for one thing. I absolutely do not agree for their use in an Aeropress - it's identical for 'pushing and flowing' Curious, I weighed ten of each: my cut ones from Chemex's unbleached FSU stock in Aeropress size (very precisely cut btw) and the original Aeropress ones. They basically weigh the same, so it isn't that (average 170 milligrams per filter for Aeropress and 180 mg/filter for Chemex, but the difference was so close the scale sometimesweighed them as the same). So, if the Chemex has slower flow, it is not because there is more paper, it would have to be something else ... but I don't believe this 'slower' thing:

I made another cup today just by reusing the FSU-100 (unbleached Chemex filter) from yesterday. I do this a lot with the regular Aeropress filters, usually it lasts four times before it gets weak points in the pulp and then I toss it. I wanted to see if the taste was different since it surprised me that it would basically taste bad compared to the potential of the coffee. I thought I might be tasting a little paper since the unbleached filters seem a little raw. Guess you can't win since bleach can add a chemical taste and raw (unbleached) can leave aftertaste from pulpmaking.

The idea was maybe the Chemex was still decent but the raw flavor was contaminating it.

The result, yes, the taste wasn't off like the first time so for me this is a problem with unbleached Chemex filters and a better test would be to run hot water through a new filter first the next time to prepare it.

But that isn't going to happen soon, because the consistency still seemed missing some of the good oils. I am not trying to slam in any way the Chemex since the filters aren't made for this, but still they say it does a better job on the 'good' oils. Definitely not for me in this experiment!

Chemex filter tea, huh? Yuck, but you are right, since I now have 99 15/16 Chemex filters I've lost hope on, a few more sixteenths of the filter can make a good untreated cellulose tea and it is worth a try to see what the 'blank' actually tastes like. But the problem with that and all my taste comments as well, is the possibility that the chemicals in the filters interact with the coffee, so the blank may give one answer and the real one might be too complicated with all that's going on to really tell ... but heck it is easy enough to check and worthwhile since I've come this far.

Hi Buzzed, and thanks for the addition. I'm reading the instructions on the box and the only wetting they recommend is for the coffee grinds themselves (and the graphic instructions are explicit), so all the water goes into the cup anyway. Still this little playing around has convinced me you are right that this will improve the taste, and maybe this is something that is well known among Chemex users, I wouldn’t know.

Now that you actually got me to read the instructions, I read the rest of the filter box, and one thing bugs me: They market this: "Chemex-bonded (R) filters filter out all bitterness, sediment, and oils: produce a clear, flavorful coffee, without fail." That bothers me because it is *all* the oils, not just some of the particularly obnoxious ones I had assumed. No wonder I thought some good stuff was missing...and:

Elsewhere, the filter's benefits are bullet-pointed on the box and include: "Absorbent special fibers for special quality"I read over this the first time, but am now thinking more about what it means. If the fibers are absorbing the oils and the filter is normally a huge 130 sq. inches, and I am using only 3.1 square inches quickly in the Aeropress, maybe my fibers saturate with the oils and that is why on subsequent uses, residual oil may pass more oil. In any case if the principle of operation is filtration by absorbing rather than by obstructing, then it is clear now to me that what I am doing is actually screwing up the Chemex filter's benefits, if any, since on top of this the longer steeping time will allow them to absorb more on 40 times the area I use, basically my use would have no benefit by Chemex definition and be a misuse of whatever science they claim. Maybe I should better understand the subtleties of how the filters are working before blowing $9 for the box and buying $16 more of junk I don't need just to get the free shipping :-(

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